25 April 2007

dCache, DPM and SRM2.2

As most of you know, the LCG experiments are requiring that all storage be accessible via the SRM2.2 interface. The current version of dCache, v1.7.0, only provides the SRM1 interface (and an incomplete SRM2.2). Full SRM2.2 support will only be available in the v1.8.0 branch of dCache. Once v1.8.0 has been fully tested and moves into production, all GridPP dCache sites will have to upgrade.

As I understand the situation, no upgrade path between v1.7.0 and v1.8.0 is planned. Sites will first have to upgrade to v1.7.1 and then move onto v1.8.0. The plan is such that v1.7.1 will contain the same code as v1.8.0, minus the SRM2.2 stuff.

Obviously all dCache sites will want to ensure that there is a stable version of the system, particularly as all sites now have 10's of TBs of experiment data on disk. The SRM2.2 bits of v1.8.0 are currently being tested. Once v1.7.1 is released we can test out the upgrade path before giving the nod to sites. There will be some additional complexity when it comes to setting up the space reservation parts of SRM2.2 in your dCache. Documentation will be available when sites have to perform this additional configuration step. In fact, all of this configuration may go into YAIM.

The situation for DPM is slightly simpler. Full SRM2.2 support exists in v1.6.4 which is going through certification at the moment (1.6.3 is the current production version). Again, there will be some additional complexity in configuring the SRM2.2 spaces, but this will be documented.

Even once the SRM2.2 endpoints are available, it is likely that the SRM1 endpoint (running simultaneously on the same host) will continue to be used by the experiments until SRM2.2 becomes widely deployed and the client tools start using it as the default interface for file access.

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